code: def test_forward(self):
      e = copy.deepcopy(EXPERIMENT)
      e = ExperimentConfig(e)
      trainer = e.experiment["trainer"]
      trainer.setup(training_metrics=trainer.training_metrics)
  
      batch = next(iter(trainer.dataset_splits.train_data_loader()))
      self.assertEqual(list(batch.keys()), ["x_in", "y_target"])
      output = trainer._forward(batch=batch)
      self.assertEqual(
          output.size()[0],
          min(len(trainer.dataset_splits.train_set), 128),
      )
      self.assertEqual(output.size()[1], trainer.model.output_dim)
  
file_path: transfer-nlp/tests/plugins/test_trainer.py
imports: import copy
  import unittest
  from pathlib import Path
  import ignite
  import ignite.metrics
  import torch.nn
  import torch.optim
  from ignite.metrics import Precision, Recall, MetricsLambda
  from transfer_nlp.plugins.config import ExperimentConfig
  from transfer_nlp.plugins.regularizers import L1
  from .trainer_utils import *
label_desc: Use image node_id 3 for calling the RegistryTest obj's underlying member method code with example usage: obj.test_forward() without return types